1. Field of the Disclosure
The present invention relates to a liquid crystal display panel and a method of fabricating the same, and particularly, to a liquid crystal display panel, which has a liquid crystal layer formed by a dropping method, and a method of fabricating the same.
2. Description of the Related Art
In general, the LCD device is a display device in which data signals corresponding to image information is supplied to a matrix of pixels. The data signals control optical transmittance of the pixels so as to display images.
The LCD device includes a liquid crystal display panel in which the pixels are arranged in a matrix and a driving part for driving the pixels.
The liquid crystal display panel includes an array substrate on which a thin film transistor (TFT) array is formed and a color filter substrate on which color filters are formed. The TFT array substrate and the color filter array substrate are attached to each other with a uniform cell gap maintained therebetween with a liquid crystal layer positioned within the cell gap.
Alignment films are formed on surfaces of the array substrate and the color filter substrate that face each other. The alignment films are rubbed to make liquid crystals to be arranged in a predetermined direction.
The array substrate and the color filter substrate are attached by a seal line formed along an outer edge of a pixel part. A polarization film and a retardation film are provided on each outer surface of the TFT array substrate and the color filter substrate. By selectively constructing a plurality of components, a liquid crystal display panel can have high luminance and good contrast characteristics by changing the direction and/or refracting the proceeding light.
Hereinafter, the liquid crystal display panel constructed as above will be described in detail with reference to the drawings.
FIG. 1 is an illustrative view schematically showing a structure of a crystal display panel according to the related art.
As shown in FIG. 1, the liquid crystal display panel includes a pixel part 35 having pixels arranged in a matrix for displaying an image, a gate pad part 31 electrically connected with the gate lines 16 of the pixel part 35, and a data pad part 32 electrically connected with the data lines 17 of the pixel part 35.
The gate pad part 31 and the data pad part 32 are formed at an edge portion of the array substrate 10, which is not overlapped by a color filter substrate 5. The gate pad part 31 supplies a scan signal from the gate driving unit (not shown) to the gate lines 16 of the pixel part 35, and the data pad part 32 supplies image information from the data driving unit (not shown) to the data lines 17 of the pixel part 35.
The data lines 17 to which image information is applied and the gate lines 16 to which a scan signal is applied are arranged to cross each other on the array substrate 10. A thin film transistor (not shown) and pixel electrodes (not shown) are provided in the regions defined by the data lines 17 and the gate lines 16.
Although not shown in FIG. 1, color filters for each of the pixels are separated by a black matrix. Further, a common electrode, which is a counter electrode of the pixel electrode formed on the array substrate 10, is formed on the color filter substrate 5.
A certain cell gap is maintained between the color filter substrate 10 and the array substrate 5 by spacers (not shown), and the color filter substrate 10 and the array substrate 5 are attached by a seal line 50 formed along an outer edge of the pixel part 35.
A certain cell gap is maintained between the color filter substrate 10 and the array substrate 5 by spacers (not shown), and the color filter substrate 10 and the array substrate 5 are attached by a seal line 50 formed along an outer edge of the pixel part 35.
The process for fabricating a liquid crystal display panel can be divided into an array process for forming a driving element on a lower array substrate, a color filter process for forming color filters on an upper color filter substrate, and a cell process for forming a unit liquid crystal display panel by attaching the array substrate and the color filter substrate. This process will be described in detail with reference to FIG. 2.
A plurality of gate lines and a plurality of data lines are vertically and horizontally formed to define pixel regions on the array substrate in the array process, and TFTs, which are the driving elements, are formed in the pixel regions and connected with the gate lines and data lines (S101). Then, pixel electrodes are formed in each of the pixel regions of the array substrate so as to be connected to the TFTs through the array process. The pixel electrodes are used to drive the liquid crystal layer when a signal is applied through the TFTs.
Red, green and blue color filters for implementing colors and common electrodes are formed on the upper color filter substrate according to the color filter process (S104).
Subsequently, alignment films are coated on the array substrate and color filter substrate, and are rubbed to provide an alignment anchoring force or a surface fixing force (namely, a pretilt angle and an alignment direction) to the liquid crystal molecules of the liquid crystal layer positioned between the array substrate and the color filter substrate (S102 and S105). Thereafter, spacers for uniformly maintaining a cell gap are spread on the array substrate. Subsequently, a sealant is coated on an outer edge portion of the color filter substrate, and then the array substrate and the color filter substrate are attached by applying pressure thereto (S103, S106, and S107).
The array substrate and the color filter substrate are formed as large-scale mother substrates. In other words, a plurality of panel regions are formed on a large-scale mother substrate, and the TFTs, which are the driving elements, and the color filter layers are formed on individual panel regions. To fabricate the individual liquid crystal display panels, the mother substrate is processed (S108) so as to cut the mother substrate into the individual liquid crystal display panels. Thereafter, liquid crystal is injected into each of the processed liquid crystal display panels through a liquid crystal injection opening, and the liquid crystal injection opening is encapsulated to form the liquid crystal layer. Then, each liquid crystal display panel is inspected to complete fabrication of liquid crystal display panels (S109 and S110).
The vacuum injection method uses a liquid crystal injection opening of a unit liquid crystal display panel separated from a large-scale mother substrate. The liquid crystal injection opening is put in a container filled with a liquid crystal in a chamber in which a certain vacuum is set. Then, liquid crystal is injected into the liquid crystal display panel according to a pressure difference between an inner side and an outer side of the liquid crystal display panel by varying a degree of the vacuum in the chamber. After the liquid crystal is filled in the liquid crystal display panel, the liquid crystal injection opening is sealed to form the liquid crystal layer of the liquid crystal display panel. Accordingly, where the liquid crystal layer is formed on the liquid crystal display panel through the vacuum injection method, one portion of each seal line must be opened to function as the liquid crystal injection opening.
The vacuum injection method as described above has the following problems.
First, it takes a long time to fill the liquid crystal into the liquid crystal display panel. In general, the attached liquid crystal display panel with an area of several hundreds cm2 has a gap of a few micrometers (μm). Thus, even with the vacuum injection method, which uses pressure difference, an injecting amount of the liquid crystal by unit time is quite small. For instance, when fabricating a liquid crystal display panel of about 15 inches, it takes 8 hours to fill the liquid crystal display panel with liquid crystal. Therefore, because it takes such a long time to fabricate the liquid crystal display panel, productivity is decreased. In addition, as the liquid crystal display panel increases in size, the time required for filling liquid crystal correspondingly increases and deficiencies in filling the liquid crystal may occur. Therefore, the vacuum injection method can hardly cope with a large-scale liquid crystal display panel.
Second, with the vacuum injection method, too much liquid crystal is consumed. In general, the actual injected quantity of liquid crystal in the vacuum injection method is very small compared to the quantity of liquid crystal filled in the container. When liquid crystal is exposed in the air or to a specific gas, it reacts with the gas and degrades. Thus, even if liquid crystal in a container is filled into a plurality of liquid crystal display panels, a large quantity of liquid crystal remaining after the filling has to be discarded, thereby increasing the overall unit price of the liquid crystal display and decreasing price competitiveness.